The Tooth Replacement Concept Utilizing Ceramic Dental Implants

Introduction
The main goal of tooth replacement is to provide our patients with a long lasting tooth-like restoration that is strong, easy to maintain, biologically compatible, and aesthetically similar to or better than natural teeth. The use of titanium in implant dentistry is a practice that is now over 50 years old and it is widely accepted that the clinical outcome of titanium implants in terms of rigid fixation and long-term functional success is good.8 However, negative aesthetic late complications including soft tissue deficiencies are widespread as well as problems with tooth contour due to lack of appropriate emergence profile management. These late complications have led to many implant collar designs and to the use of white zirconia trans-gingival abutments, as well as meticulous provisionalization protocols to sculpt the soft tissues, all in an attempt to minimize soft tissue recession and maximizing tissue conditioning to attain desirable emergence profiles. Although these techniques can yield acceptable aesthetic results, due to the clinical time and expense needed to perform these procedures they are seldom done in the anterior maxilla and almost never in other sites.

The tooth replacement concept introduced by the Drs. Oliva1-3 focuses on the utilization of one-piece, zirconia all ceramic dental implants in treating the partially edentulous. This concept evolved because of the need to simplify the restorative protocol and enhance biological stability as well as idealize and simplify emergence profile formation. At its core, the tooth replacement concept uses an innovative one-piece, highly roughened, tooth shaped, one-piece zirconia implant. The implant has shown high degrees of clinical success.5 As far as the material, zirconia is a strong ceramic that shows rates of osseo-integration similar to that of titanium.13 The CeraRoot system has seven implant shapes each with very specific tooth replacement indications (Fig. 1). The emergence profile is thus tooth specific and if the surgical placement is followed correctly then the prosthetic rehabilitation is simplified. The following case follows the replacement of teeth #35 and #36 with CeraRoot 14 and CeraRoot 16 implants, respectively, and a final restoration made of functionally monolithic zirconia crowns.

FIGURE 1. CeraRoot implants.
The CeraRoot implant system has seven implant shapes each corresponding to a tooth being replaced. Each implant has specific tooth replacement indications and comes in a variety of lengths.

Presentation:
Diagnosis
The patient, a 67-year-old female non-smoker in good general health, presented with a missing tooth #36 and a fractured crown on tooth #35 (Fig. 2). History revealed that tooth #36 was extracted due to failed endodontic treatment and that the fracture of the #35 post-core and crown occurred during mastication. Due to the lack of ferrule and poor prognosis of #35, the option to follow crown lengthening, post-core and crown was discussed, and rejected. Radiographic and clinical exam revealed that bone volume was adequate in all dimensions and soft tissue was thick and keratinized (Fig. 3). Occlusion was stable and adequate restorative space was available.

FIGURE 2. Pre-operative radiograph.
Periapical showing the edentulous site of tooth #36 and the endodontically treated root of #35.

FIGURE 3. Pre-operative top view.
Pre-operative condition. Adequate mesiadistal and buccal lingual bone volume can be visualized as can the quality and volume of the well-keratinized tissue.

Treatment Plan
As the patient wanted a fixed restoration, options were discussed including an option of a conventional four unit fixed partial denture or implant-retained crowns. The span for a bridge was too large and tooth #37 was not an optimal abutment. An implant-supported reconstruction was the preferred treatment option. The possibility of the use of a zirconia one-piece dental implant (CeraRoot, Oral Iceberg, Granollers, Spain) was discussed and the alternative titanium implant option was also discussed. Due to the restorative simplicity and the patients desire for the most tooth-like replacement option, a ceramic tooth replacement approach was followed.

The size of the CeraRoot implant presented an increased surface area for osseointegration, especially since we would be placing the implant immediately after extraction in the #35. The trans-gingival collar of the CeraRoot implant would provide us with a built-in emergence profile making the final prosthetic protocol simple and functional with very little in terms of prosthetic complications. The final treatment would involve the extraction of #35, immediate placement of two CeraRoot implants and provisionalization using an Essex Retainer (Raintree Essex, Densply). After the rigid fixation of the implants, full contour aesthetically layered zirconia crowns would be used as final restorations.

Surgical Treatment
The patient was pre-medicated with an antibiotic (Amoxicllin 500mg), which was to be continued for seven days post-operatively as well as Decadron (Dexamethasone, 10mg) with a three day tapering dosing regiment. Two carpules of four percent Articaine 1:200,000 epinephrine (Septocaine, Septodont Inc., France) were infiltrated and used to anesthetize the operative area. An atraumatic extraction of the root of #35 was preformed using surgical elevators and forceps and the socket thoroughly curetted. No flap was raised during the extraction. The osteotomy was preformed utilizing very efficient ceramic drills at a maximum speed of 300RPM, the slow drilling helps maintain the vitality of the bone. No irrigation was used during the drilling and bone debris was collected from the drills. The site of #36 was prepared using a tissue punch and a slow drilling protocol. The final preparation of the osteotomy was done with the countersink drills (Fig. 4). Careful attention was paid to preparing the implant site to accommodate the wide diameter of the prosthetic emergence. The shoulder of the implant was placed at the desired tissue level. The prosthetic table of CeraRoot 14 is oval, mimicking the emergence of an upper premolar, and thus a specialized technique to contour the coronal aspect of the osteotomy was used to precisely prepare the bone.2 The CeraRoot 16 implant at the #36 site was threaded int
o place and achieved excellent stability at over 50Nm with the buccal restorative margin placed where desired, about 0.5mm below the gingival margin. The CeraRoot 14 implant was press fit and tapped into final position again with the restorative platform just apical to that of the original tooth (Figs. 5-8). The facial of the extraction site, and the circumferential gap between the implant and the bone, was grafted with the autogenous bone chips. The radiographic image (Fig. 8) showed good placement, the apical portion of the anterior implant was very close to the apex of tooth #34 as a result of overcorrection of the angulation on the implant. Clearly visible is the fact that the PDL of the first bicuspid was not violated and tooth #34 remained vital and asymptomatic. No sutures were needed as no flap was raised. A Periotest M (Medizintechnik Gulden, Germany), a wireless device used to provide an objective evaluation of an implant’s stability, was used to assess a baseline for stability (Fig. 9). The readings for teeth #35 and #36 were –5.7 and –6.7 respectively. The absolute range for the Periotest M is –8.0 to +50. The more negative the reading the greater the stability/dampening effect of the measured tooth. The temporization was subsequently accomplished with a removable essex appliance that was to be worn 24/7 until healing was completed.

FIGURE 4. Countersink drills.
The ceramic counter sink drills are shown. The CeraRoot 16 countersink prepared the coronal emergence of the implant. The diameter of the prosthetic table is 8mm. For the CeraRoot 14 the emergence needs to be formed to accommodate an oval implant whose prosthetic table measures 7mm by 5mm. This careful preparation is achieved using the countersink drill.

FIGURE 5. Surgery top.
View of the placement of the two implants in ideal location mesiodistally and angulation. The restorative result can be easily visualized.

FIGURE 6. Surgery buccal.
Placement of the restorative margins is equigingival or slightly sub gingival. This makes the prosthetic steps very easy to accomplish as tissue can be retracted with cord or ablated using radio-surgery or laser.

FIGURE 7. Surgery lingual.
View of placement from the lingual showing the shape of the restorative abutment. This abutment was designed to mimic an ideal tooth preparation. The taper and size of the abutment can be modified if needed to account to different clinical situations.

FIGURE 8. Radiograph day of surgery.
Apex of the anterior implant is near the apex of tooth #34. No contact is evident and the PDL is preserved. The inter-proximal margin of the prosthetic table seems like it is at osseous level due to the angulation of the X-ray and the radio-opaque bone graft.

FIGURE 9. Periotest M.
Device used to objectively assess the stability/dampening ability of the implant. The Periotest M was designed to be used with teeth or implants. The value on its own is not entirely prognostic, however, the development of trends over time is very telling in terms of healing and achievement of rigid fixation.

Prosthetic Treatment
After 12 weeks, the soft tissue healed and the implant integrated and was now ready for final restoration (Figs. 10-12). Once again a Periotest M (Medizintechnik Gulden, Germany) was used to assess the stability of the implants, the readings for teeth #35 and #36 were –6.9 and –7.4, respectively. No preparation of the restorative margin was required as the margins were very well placed. If needed, this could have been accomplished prior to final scanning (Fig. 10). Retraction was accomplished using #00 cord (Ultradent, South Jordan, UT) and a digital scan utilizing the iTero scanner (Cadent, NJ) was taken (Figs. 13,14). Two Prettau zirconia crowns were fabricated with zirconia in all functional areas and porcelain added on the buccal of the crown for aesthetics (Figs. 15-17). This assured that the functional areas would be resistant to chipping and wear. The crowns were tried in and inserted with a Glass Ionomer cement (GC FujiCEM 2, GC America). Excess cement was carefully cleaned. Occlusion was adjusted as to avoid lateral contacts and allow shim stock clearance.

FIGURE 10. Healed top.
Top view of the implants after 12 weeks of healing. Soft tissue maturation is apparent. Visible is the restorative margin. The prosthetic rehabilitation can now proceed as if this were a tooth.

FIGURE 11. Healed Buccal
Interproximal tissue is maint
ained and soft tissue in general is healthy and maintained its form and texture. The soft tissue around the implants is identical to that around the natural teeth.

FIGURE 12. Radiograph after healing.
Minimal bone remodelling is visible. The improved angulation also demonstrated the bone level between the implants.

FIGURE 13. iTero Model occlusal.
Occlusal view of the iTero model. The mesial margin of the molar was not entirely exposed as to create a “platform switch” and allow for thicker soft tissue between the implants.

FIGURE 14. iTero model buccal.
Lateral view of the working model. Adequate interocclusal space is available for the rehabilitation. No preparation of the abutments was necessary.

FIGURE 15. Final top.
Occlusal view of the completed crowns. Prettau zirconia can be artfully stained to achieve a very aesthetic occlusal anatomy that is chip and wear resistant.

FIGURE 16. Final lingual.
Beautiful integration of the crowns with the soft tissue and the neighbouring teeth. The contours of the finished crowns are very natural.

FIGURE 17. Final buccal.
Soft tissue immediately after cementation. This figure shows the natural emergence profile leading to restorations that are anatomically contoured.

FIGURE 18. One-year radiograph.
Radiograph showing the final restoration. The implant and crown form an almost continuous unit. On the mesial of the molar one can see the “platform switch” which allows for thicker soft tissue formation between the implants.

The superior final result and one year post-op pictures show the beautiful soft tissue response to the CeraRoot surface (Figs. 19, 20). The bone remodeling during healing did not result in any topographical boney changes, Figure 22 shows the radiographic projection taken at 12 months post-op compared to the radiograph taken at the three month mark, showing minimal inter proximal remodeling of bone. Soft tissue stability and re-establishment of inter proximal soft tissue can be validated on the 12 month post-op photographs (Fig. 21). Periotest M values at 12 months post-op where –7.2 and –8.0 for the #35 and #36 respectively showing excellent stability maintained during function.

FIGURE 19. One-year lingual.
Soft tissue contours are stable over the course of the first 12 months. More inteproximal tissue fill is evident.

FIGURE 20. One-year buccal.
Over the course of one year, we see that the scalloping of the tissue between the implants is stable over time.

FIGURE 21. Buccal comparison.
Upper view is immediately after cementation. Lower is at 12 months. Over the course of a year we see formation of thicker soft tissue between the implants and thus a more mature papilla. This occurs when the natural contour of teeth can be maintained. The patients can no longer distinguish between her tooth and implants.

FIGURE 22. Radiographic comparison.
Upper view is at the end of healing, lower at 12 months. Over the course of a year, little remodeling occurred. The red arrows show the interproximal forming a shape that is very similar to what we see between healthy teeth. This topography is present when biologic width is respected, as it is around natural teeth. This is a clear benefit of the one-piece design on these implants.

Discussion
When treating the completely edentulous patient, the application of the metal two-piece implants is appropriate. However, the use of two-piece metal implants in treating the partially edentulous patients presents some clinical complications that in the author’s opinion have been ignored for some time. The complexity of creating and maintaining tissue contours and health around the implant abutment complex is an ever-elusive aspect of modern implantology. The author has found a very high degree of clinical success being achieved using an all-ceramic Zirconia, one-piece dental implant. With the emergence profile being designed as part of a white, tissue level implant we see less peri-implant disease and less mechanical and aesthetic soft tissue complications. The great aesthetic potential and restorative simplicity make the CeraRoot implant system ideal for tooth replacement (Fig. 23). Periodontal health is amplified by the absence of a connection and micro-gap, and the affinity of the gingival complex to the zirconium oxide surface. This case presented an example of where the tooth replacement concept can be simply and cost effectively applied with great success.
 
FIGURE 23. Top view comparison.
From the onset of treatment to the cementation of the crowns 14 weeks elapsed. This demonstrated the restorative simplicity gained by precise placement of the implants and the capacity of the soft tissues to heal in a most natural manner.

With many manufacturers exploring this new paradigm of tooth replacement, it is this authors opinion that the one-piece ceramic implant is becoming the treatment of choice for the partially edentulous patients.OH

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Dr. Dan Hagi received his dental training at the University of Toronto and now maintains a multidisciplinary implant and rehabilitative practice in Thornhill, Ontario. He is an associate Fellow of the American Academy of Implant Dentistry(AAID), a Fellow of the International Congress of Oral Implantology(ICOI), the Academy of General Dentistry (AGD), the Academy for Dental Facial Esthetics (ADFE) and the Misch International Implant Institute(MIII). His private practice focuses on metal free, minimally invasive implant rehabilitation and aesthetic smile design. He is a lecturer and mentor as well as a consultant on emerging metal-free materials and techniques.

Oral Health welcomes this original article.

References:

1. Oliva J, Oliva X, Oliva JD. Zirconia implants and all-ceramic restorations for the aesthetic replacement of two central incisors. EJED 2008;3(2):175-185.

2. Oliva J, Oliva X, Oliva JD. Ovoid Zirconia Implants: Anatomic Design for Premolar Replacement. Int J Period Rest Dent 2008; 28:609-615.

3. Oliva J, Oliva X, Oliva JD. Replacement of congenitally missing maxillary permanent canine with a zirconium oxide dental implant and crown. A case report from an ongoing clinical study. Oral Surgery 2008;1(2):140-144.

4. Oliva J, Oliva X, Oliva JD. Full mouth oral rehabilitation in a titanium allergy patient using zirconium oxide dental implants and zirconium oxide restorations A case report from an on-going clinical study. EJED; 2010 Summer; 5(2):190-203.

5. Oliva J, Oliva X, Oliva JD. Five year success rate of first consecutive 831 zirconia dental implants in humans. A comparison of three different rough surfaces. JOMI 2010 Mar-Apr;25(2):336-44.

6. Akagawa Y, Hosokawa R, Sato Y, Kamayama K. Comparison between freestanding and tooth-connected partially stabilized zirconia implants after two years’ function in monkeys: a clinical and histologic study. J Prosthet Dent.1998 Nov;80(5):551-8.

7. Akagawa Y, Ichikawa Y, Nikai H, Tsuru H. Interface histology of unloaded and early loaded partially stabilized zirconia endosseous implant in initial bone healing. J Prosthet Dent. 1993 Jun;69(6):599-604

8. Lekholm U, Gröndahl K, Jemt T. Outcome of oral implant treatment in partially edentulous jaws followed 20 years in clinical function. Clin Implant Dent Relat Res. 2006;8(4):178-86.

9. Mobilio N, Stefanoni F, Contiero P, Mollica F, Catapano S. Experimental and numeric stress analysis of titanium and zirconia one-piece dental implants. Int J Oral Maxillofac Implants. 2013 May-Jun;28(3):e135-42.

10. Andreiotelli M, Wenz HJ, Kohal RJ. Are ceramic implants a viable alternative to titanium implants? A systematic literature review. Clin Oral Implants Res. 2009 Sep;20 Suppl 4:32-47.

11. Saulacic N, Erdösi R, Bosshardt DD, Gruber R, Buser D. Acid and Alkaline Etching of Sandblasted Zirconia Implants: A Histomorphometric Study in Miniature Pigs. Clin Implant Dent Relat Res. 2013 Apr 9.

12. Delgado-Ruiz RA, Calvo-Guirado JL, Abboud M, Ramirez-Fernandez MP, Mate-Sanchez JE, Negri B, Rothamel D. Histologic and Histomorphometric Behavior of Microgrooved Zirconia Dental Implants with Immediate Loading. Clin Implant Dent Relat Res. 2013 Apr 5.

13. Oliva X, Oliva J, Oliva JD, Prasad HS, Rohrer MD. Osseointegration of Zirconia (Y-TZP) Dental Implants: A Histologic, Histomorphometric and Removal Torque Study in the Hip of Sheep. Int J Oral Implantol Clin Res 2013;4(2):00-00.